This invention relates to a thermal transfer sheet and printed matter. More specifically, the invention relates to a thermal transfer sheet capable of suppressing the occurrence of static electricity during transfer onto a material as a transfer image support, and printed matter excellent in antistatic properties.
It has been done to form a gradation image, or a monotone image, such as a character or sign, on a substrate by a thermal transfer process. As the thermal transfer process, sublimation transfer and fusion transfer are used widely.
Of these methods, the sublimation transfer method comprises using a thermal transfer sheet which has, carried on a base sheet, a dye layer containing a sublimation dye as a coloring material fused or dispersed in a binder resin; superimposing this thermal transfer sheet on a substrate; and applying energy corresponding to image information to a heating device, such as a thermal head, to migrate the sublimation dye contained in the dye layer on the thermal transfer sheet to the substrate, thereby forming an image. This sublimation transfer method can control the amount of migration of the dye on a dot basis depending on the amount of the energy applied to the thermal transfer sheet, and is thus excellent in the formation of a gradation image.
Many cards, including identification card, driver's license, and membership card, have been used. These cards have records of various pieces of information which specify the status of the owner, etc. For ID cards, in particular, an image of a photograph of the face is the most important information in addition to character information such as the address and name. Recording of information in such cards is made by the use of the above-described sublimation transfer method which facilitates the formation of various images, characters and signs.
However, a gradation image or a monotone image formed by the sublimation transfer method may undergo fading, because the transferred dye is present on the surface. To avoid this drawback, and prevent forgery or doctoring of image information, a protective layer is provided on the image formed.
As means of forming such a protective layer, there is a method involving the transfer of a protective layer onto a formed image by the use of a thermal transfer sheet provided with a transfer layer. Transfer of this protective layer is carried out using a thermal printer. However, this method has posed the problem that a large amount of static electricity develops during peeling of the protective layer from the thermal transfer sheet, thereby causing poor transport of a material as a transfer image support, or of a thermal transfer sheet, within the thermal printer.
To solve this problem, the customary practice has been to provide an antistatic layer on, or contain an antistatic agent in, the material as a transfer image support, thereby suppressing the occurrence of static electricity during transfer of the protective layer. However, even when the material as a transfer image support is provided with antistatic means, it is difficult to prevent static electricity generated during the peeling of the protective layer from the thermal transfer sheet. Furthermore, the transferred material after transfer of the protective layer has the most facial surface which is not the antistatic layer or the surface containing the antistatic agent. Thus, deposition of static electricity on the transferred material cannot be prevented effectively.